/Engine/Source/Editor/StaticMeshEditor/Public/StaticMeshEditorSubsystem.h
Create a new Actor in the level that contains a duplicate of all the Actors Static Meshes Component. The ActorsToJoin need to be in the same Level. This will have a low impact on performance but may help the edition by grouping the meshes under a single Actor.
The new created actor.
[AActor](API\Runtime\Engine\GameFramework\AActor) * JoinStaticMeshActors ( const [TArray](API\Runtime\Core\Containers\TArray)< class [AStaticMeshActor](API\Runtime\Engine\Engine\AStaticMeshActor) * > & ActorsToJoin, const [FJoinStaticMeshActorsOptions](API\Editor\StaticMeshEditor\FJoinStaticMeshActorsOptions) & JoinOptions )